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WorksheetsASTRO 1010 Final
Total questions: 150
Worksheet time: 1hrs 15mins
Which of the following statements about electromagnetic radiation is FALSE?
different waves of electromagnetic radiation differ in their wavelength or frequency
it is typically produced when charged particles oscillate
it always spreads out at the speed of light
it is given off by all objects that are not at a temperature of absolute zero
the radiation consists of tiny charged particles given off by the nuclei of atoms
How fast do electromagnetic waves travel?
at the speed of sound
at different speeds, depending on the temperature of the atoms that produce them
they always have zero speed
at the speed of charge
at the speed of light
This chapter discusses that light sometimes acts like a photon. What is a photon?
a self-contained “packet” of electro-magnetic energy
a kind of magnetic substance found in reflective minerals
you can’t fool me. Einstein showed that photons were a mistake – they don’t exist.
a kind of sound that is too high frequency for the human ear to hear
a charged particle in the nucleus of every atom
In the future, several students living on board a space station decide to have a race among different types of electromagnetic radiation. Which of the following travels through space the fastest? (consider space as a perfect vacuum)
x-rays
you can't fool me, all of these travel through space at the same speed
radio waves
infrared
visible light
Which of the following has the longest wavelength?
ultraviolet waves
x-rays
radio waves
visible light waves
you can't fool me, all these have the same wavelength
What is the chief factor that determines what type of electromagnetic radiation objects give off?
size
temperature
distance from the Earth's core
mass
composition
Which of the following has the greatest average energy of random atomic and molecular motion?
a cube of ice
a cube of steam
a cube of the Sun
a cube of air (on Earth)
a cube of water
An astronomer discovers a new star and wants to measure its temperature. She would typically do this by:
making a blackbody curve and finding the wavelength of the peak (maximum)
measuring the intensity of radio waves the star gives off
measuring how much light the star reflects
sending a graduate student with a very long (and durable) thermometer to the star's vicinity
measuring the Doppler shift of its spectral lines
Wien's Law relates the wavelength at which a star gives off the greatest amount of energy to the star's
temperature
overall color
motion toward us or away from us
magnetic field
none of the above
Why is an absorption spectrum especially useful for astronomers?
It has dark lines in it that allow astronomers to determine what elements are in the star
It helped astronomers to understand the rainbows we see on Earth after storms
An absorption spectrum is not useful to astronomers at all. When they see one, it means they cannot learn anything about the stars that produced the annoying absorption.
It has bright lines in it which allow astronomers to determine how bright the star is
It shows that the stars are transparent; we can see right through them
One of the great triumphs of spectroscopy was when astronomers identified a new element in the Sun (one that was only later found on Earth). Today, this element is called:
Solarium
Helium
Astronimum
Einsteinium
Hydrogen
Why do different types of atoms (elements) give off or absorb different spectral lines?
all elements have the same lines, but they are Doppler shifted by different amounts
because some atoms do not have a ground state, while others have three or four
in some elements, electrons can only move to odd numbered levels, in others only to even numbered ones
because the spacing of the energy levels is different in different atoms
in heavier elements, diffraction spreads out the lines that the atom produces, making the colors different
What happens as an electron falls from a higher level to a lower level in an atom?
a photon is given off
a photon is absorbed
another electron form the lower level takes its place
the color of the wave involved shifts to the red
nothing happens; electrons can only go from a lower level to a higher level
We observe a glowing cloud of gas in space with a spectroscope. We note that many of the familiar lines of hydrogen that we know on Earth seem to be in a different place. They are shifted toward the blue or violet end of the spectrum compared to their positions in the spectrum of glowing hydrogen gas on Earth. From this we can conclude that:
the cloud is moving toward us
the cloud is much hotter than hydrogen on Earth
the cloud is moving away from us
the cloud is much cooler than hydrogen on Earth
none of these can be concluded from this observation
A fashion designer decides to bring out a new line of clothing which reflects the longest wavelength of visible light. What color will these articles of clothing be to the human eye?
black
red
white
green
blue
Astronomical observatories have been available since ancient times, and many cultures set aside special sites for astronomical observations. The thing modern observatories have that was missing from these older observatories until about 1610 was:
assistants for sharing the astronomer's work
a method of keeping good records
computers
a dark site where light did not get in the way
telescopes
The most important function of an astronomical telescope is to:
collect as much light as possible and bring it to a focus
pierce through the clouds so a cloudy night is not wasted
bring distant objects closer by pulling on the light
magnify (enlarge) celestial objects so we can see them clearly
enhance the violet colors of an object, which our eyes have trouble seeing
The first person who regularly turned a telescope to astronomical observations (and published his observations) was
Adam Refractor
Edwin Hubble
Isaac Newton
Karl Janskey
Galilieo Galilei
The size of the device that collects radiation (such as light) is called a telescope's:
resolution
focal width
aperture
magnification
criterion
When a knowledgeable amateur astronomer tells you that she has a 14-inch telescope, what does the number 14 refer to?
the number of times the image is magnified
the length of the telescope tube
the diameter of the primary lens or mirror
the focal length
the length of the eyepiece tube
largest visible-light telescopes in the world use what device to collect as much light as possible before the light is brought to a focus (to act as the "light bucket")?
a spectroscope
a lens
a CCD
a mirror
a valley in Puerto Rico
A new technique called adaptive optics allows astronomers to:
change the eyepieces of their telescopes much more quickly than ever before
use the observatory shop to make better eye-glasses for their graduate students
change the region of the electro-magnetic spectrum in which their telescope is able to detect radiation
compensate for changes in the Earth's atmosphere and achieve better resolution
increase the aperture of their telescopes by connecting several telescopes
At the largest and most modern astronomical observatories on Earth today, which of the following regularly happens to the image formed by the telescope?
it is viewed by a group of graduate students who then make a sketch of it to have a permanent record
it is sent to the FBI so they can check for evidence of nefarious deeds
it is recorded using an electronic detector called a CCD for later analysis
it is recorded on a piece of black & white film, which is then developed in a bath of chemicals
it is reflected by a special arrangement of mirrors back into the beam and up into the sky
To break up light into the component colors that it contains, astronomers use a device called:
a spectrometer
an interferometer array
a CCD
a Cassegrain spliter
a telescope
The two regions of the electromagnetic spectrum where the Earth's atmosphere is transparent (radiation can get in) are visible light and:
you can't fool me, the atmosphere is transparent ONLY for visible light
x-ray
ultraviolet
gamma ray
radio
What was the major problem with the Hubble Space Telescope when it was first launched into orbit?
the mirror cover was stuck in the “partly on” position, making part of the mirror not usable
its spectroscope broke during the launch
it was in the wrong orbit, so it dipped down into the Earth's thicker atmosphere regularly
its antenna wouldn't open, so the data could not be sent back to Earth
the mirror's shape was slightly wrong, so all the light did not come to a single focus
Why do astronomers prefer to put infrared telescopes on high-flying airplanes or on satellites in space?
because high up the Sun's energy can be used to heat the infrared telescope
because no infrared radiation can exist anywhere near the Earth's surface
because that way they are significantly closer to the objects they observe
because the water vapor in the lower atmosphere is very good at absorbing infrared
You can't fool me, all infrared telescopes are located on the Earth's surface
Which of these is a distinguishing characteristic of the James Webb telescope?
it is about the same size and design as the Hubble Space Telescope, which is wearing out
it allows us to take pictures with the same resolution as a radio dish
it has the largest mirror ever put into space for observing faint objects
it is in low Earth orbit, and thus easy for astronauts to repair
it can observe gamma-rays from the most energetic events in the universe
The Chandra Observatory orbiting the Earth is designed to
spy on countries in Asia, such as India, China, and Pakistan
replace the Hubble Space Telescope, with a much larger mirror for collecting visible light
examine sources of cosmic x-rays
search for rapidly changing radio signals
search for infra-red waves from stars that are in the process of being born
The SOFIA Project was
an x-ray telescope flying many kilometers up (so high that it had to be automated)
a NASA aircraft used only by Hollywood movie-makers to teach what it's like in free fall
a balloon designed to fly above the ozone layer and search for ultraviolet radiation from space
a small Lear jet with an 8-inch visible-light telescope on board, designed to search for lost NASA spacecraft
an airplane with an infra-red telescope on board designed to fly above much of the water vapor in the Earth's atmosphere
As astronomers have learned more about the structure of the Sun, they have found that it
is made of billions of individual pieces of hot rock, all orbiting around each other in a whirling arrangement
is made entirely of liquid, with a tiny bit of hot gas on the outside
is solid throughout, but with a large very hot atmosphere
has a small solid core inside
is made entirely of hot gas
You are out on the beach, enjoying the warm sunshine with friends. As you glance up at the Sun (only briefly we hope), the part of the Sun that you can see directly is called its:
chromosphere
core
photosphere
heliopause
corona
The most common element in the Sun is
water
hydrogen
nitrogen
iron
helium
The hottest zone of the Sun is the
chromosphere
core
radiative zone
photosphere
convection zone
The Sun's photosphere is
the hottest region of the Sun
the outermost layers of the Sun’s atmosphere
the central region where the energy of the Sun originates
the part of the Sun from which the light comes that we see when we look at the Sun with our eyes
the first region you would come to when leaving the core
The Sun's chromosphere and corona were discovered
in the late 19th century through the use of a spectrograph
using spacecraft that orbited Venus, a planet with a better view of the Sun
using the first telescopes Galileo built
during total eclipses of the Sun
by ancient shepherds, who saw reflections of the Sun in quiet pools of water
The Sun's chromosphere contains many jet-like projections that stick up into the transition region. These spikes of gas are called:
flares
coronae
spicules
plages
prominences
What mechanisms do astronomers believe is responsible for making the Sun's outer atmosphere so much hotter than its photosphere?
The Sun's magnetic field interacting with the charged particles that make up the atmosphere
the ionization of a new element called coronium
stirring by comets, meteors, and other pieces of solid material being pulled in by the Sun's strong gravity
light reflected back from the terrestrial planets
astronomers really don't have even a guess about what heats the Sun's outermost layers
Solar wind particles can be captured by the Earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for:
aurorae (northern and southern lights)
tropical storms (regions of rapidly rotating air)
the greenhouse effect
the reddish color we see during sunsets
the poor quality of television programming in the world's northern hemisphere
The granulation pattern that astronomers have observed on the surface of the Sun tells us that:
the solar wind must consist of very small (low-mass) particles
the Sun's surface is made of a thin solid that cracks easily
the Sun accumulates a lot of dirt and dust because of its large gravity
the Sun is a lot cooler on the inside than on the outside
hot material must be rising from the Sun's hotter interior
Sunspots are darker than the regions of the Sun around them because
they are located in the corona and not on the photosphere
they consist of different elements than the rest of the Sun
they move much faster around the Sun than other material and thus heat up
they are the shadows of the planets and asteroids seen on the bright surface of the Sun
they are cooler than the material around them (although still very hot compared to Earth temperatures)
What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker?
Sunspots are regions in the upper chromosphere where there is a lot of coronium, which absorbs light
Sunspots are so mysterious and difficult to explain, astronomers really don’t have idea what causes them
Sunspots are regions where carbon clouds high above the photosphere gather and these dark clouds block the light from underneath them
Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath
Sunspots are holes (less dense regions) in the Sun’s photosphere, through which we can see the darker regions of the Sun below
When we use the light of atoms such as hydrogen and calcium to examine the Sun's outer layers, we can see bright "clouds" in the chromosphere right around the location of sunspots. These bright clouds are given the name:
plages
active regions
granules
Zeeman rings
spot umbras
Recently, some engineers and scientists have proposed building spaceships with enormous "sails" that catch the solar wind and use it to move the ship. What kinds of particles would be hitting this sail (i.e., what is the solar wind mostly made of):
calcium atoms
scientists do not have any idea of the composition of the solar wind; it is very mysterious
electrons and protons
nuclei of heavier atoms such as iron and nickel
gamma-rays
Coronal Mass Ejections from the Sun have many serious effects on or near the Earth. Which of the following is NOT one of these effects?
exposing astronauts and airplane passengers to increased amounts of radiation
heating the ionosphere and thus expanding the extent of our planet’s atmosphere
causing power surges and power outages in parts of the Earth near the poles
disrupting the electronics of satellites
causing huge cyclones around the equator of the Earth
Physicists Kelvin and Helmholtz in the 19th Century proposed gravitational contraction as a possible explanation for:
the length of the astronomical unit
the energy source of the Sun
the age of the Sun
the radius of the Sun
coronal mass ejections (CMEs)
Today we realize that the source of energy for the Sun is a process called
radioactivity
nuclear fusion
mechanical to thermal energy conversion
dilithium crystal moderation
Kelvin-Helmholtz contraction
According to the formula E=mc2
energy can travel much faster than light (in fact its speed can be the speed of light squared)
when two masses collide, we always get a lot of light
a little bit of mass can be converted into a substantial amount of energy
Einstein had a cool stage name
mass has to travel at the speed of light before it can produce any energy
Which of the following is NOT one of the fundamental particles that we typically find inside atoms?
neutrons
positrons
electrons
actually, all of these are typically found inside atoms
protons
The antimatter version of an electron is called a
proton
antitron
gammatron
neutrino
positron
In the Sun, when a positron and an electron collide, they will produce:
hydrogen
energy in the form of a gamma ray
a neutrino
a deuteron
a neutron
A college friend of yours who has been postponing taking any science courses hears you talking about the generation of nuclear energy in the Sun and makes the following observation: "The whole idea of the atomic nucleus is pretty ridiculous. If an oxygen nucleus consists of eight protons and eight neutrons, the charge on that nucleus is positive. Since even I learned in high school that like charges repel, such a nucleus would find all its positive protons repelling and quickly fall apart." How would you answer his argument?
the electrons outside the nucleus repel the protons and keep them inside the nucleus
there is no answer; scientists do not have a clue about how the nucleus manages to keep itself together
the neutrons in the nucleus are negative, so they cancel the positive charge on the protons
gravity is much stronger than electric repulsion and holds every nucleus together
the nuclear force, which is attractive over short distances like the nucleus, and stronger than electricity, holds the nucleus together
Which of the following has the lowest mass?
a neutron
a proton
a hydrogen atom
an electron
a neutrino
When two light elements collide to undergo nuclear fusion,
the result is always to make nuclei of iron
the positive charges in the nuclei attract, pulling the nuclei together faster and faster
some of the mass is converted into energy
the total mass involved increases
only one survives; the other turns into a release of pure energy
Where in the Sun does fusion of hydrogen occur?
pretty much throughout the entire body of the Sun
only in the core
only in the layer where there is a lot of convection going on
only near the photosphere (its visible surface layer)
nowhere
Who pays the bill for the energy generated by nuclear fusion in the Sun? In other words, where does the energy pouring out of the Sun come from ultimately?
tax payers
heavy nuclei are breaking apart into lighter nuclei
a little bit of mass is lost in each fusion reaction and is turned into energy (the Sun is losing mass)
material (like meteorites) is falling into the Sun and being vaporized to produce energy
the Sun is spinning more slowly as time goes on; rotation energy is lost
The Sun is an enormous ball of gas. Left to itself, a ball of so many atoms should collapse under its own tremendous gravity. Why is our Sun not collapsing?
nuclear fusion in the core keeps the temperature and the pressure inside the Sun at a high enough level so that gravity is balanced
neutrinos from the core exert an enormous pressure on the layers of the Sun as they travel outward; this pressure is more than enough to keep our star from collapsing
the pressure of the corona keeps the Sun's main body of gases confined to a small volume
the gravity of the planets around the Sun pulls its material outward, preventing collapse
you can't fool me, the Sun is shrinking all the time, it just happens very slowly
The material inside the Sun's core is in the form of a
a ball of iron atoms
liquid
plasma
solid
none of these
When energy is first produced by fusion deep in the core of the star, that energy moves outward mostly by what process?
radiation
conduction
theoretical modeling
convection
none of these
Which of the following, produced at the core of the Sun, will take the shortest time to emerge from the Sun's photosphere (surface)?
a deuteron
a photon
a neutrino
a positron
a proton
When an astronomer rambles on and on about the luminosity of a star she is studying, she is talking about:
what color the star is
the elements she can see in the star's spectrum
how much energy the star gives off each second
the total amount of mass in the star
the star's apparent size (the size seen from Earth)
Using a good pair of binoculars, you observe a section of the sky where there are stars of many different apparent brightnesses. You find one star that appears especially dim. This star looks dim because it is:
a very low luminosity
very far away
it could be more than one of the above; there is no way to tell which answer is right by just looking at the star
partly obscured by a cloud
radiating most of its energy in the infrared region of the spectrum
An exhausted-looking astronomer comes off the mountain where her observatory is located and tells you she has been doing photometry all night. What has she been up to?
counting the number of stars in different star clusters (groups)
taking photos through bedroom windows in the valley below
putting the light of stars through a spectrograph to measure what elements are present
measuring the brightness of different stars
measuring the positions of stars on photographic plates taken over many years
Which of the following looks the brightest in the sky? (These are apparent magnitudes)
a star with magnitude 6
a star with magnitude 10
a star with magnitude -1
a star with magnitude 1
you can't fool me, all of the above look equally bright from Earth
Which color star is likely to be the hottest?
orange
yellow
blue
green
red
Which of the following types of star is the coolest (has the lowest surface temperature)?
M
O
F
A
G
A team of astronomers takes spectra of thousands of different stars in different parts of the sky. The spectra show significant differences. The main reason the spectra of the stars do not all look alike is that the stars
are made of significantly different elements
change their spectra as they age, and so young stars have very different spectra from older ones
sometimes have atmospheres and sometimes do not
have different temperatures
are located in many different regions of the Milky Way
Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of:
increasing amount of hydrogen
you can't fool me, there is no order to the spectral types (that's why the letters are not in alphabetical order)
decreasing distance from us
increasing mass
decreasing surface temperature
After a lot of work, a group of graduate students has finally measured the wavelengths of many dozens of lines in the spectrum of a distant star. If a number of the lines come from molecules such as titanium oxide, the star is likely to be which spectral type:
we need more information; lines from molecules can be found in stars of every spectral type
O
B
M
A
The astronomer who, at the turn of the century, measured the spectra of hundreds of thousands of stars, leaving a catalog that astronomers used for the rest of the century, was:
Edwin Hubble
Annie Cannon
Cecilia Payne
Joseph Fraunhofer
James Lick
Some objects in space just don’t have what it takes to be a star (just like many hopefuls in Hollywood don’t.) Which of the following is a “failed star”, an object with too little mass to qualify as a star?
an O-type star
an M-type dwarf
any star with high proper motion
a brown dwarf
the Sun
At an astronomical conference, an astronomer gives a report on a star that interests astronomers because of hints that it may have a planet around it. In his report the astronomer gives the average speed with which this star is moving away from the Sun. How did the astronomer measure this speed?
by looking at the Doppler shift in the lines of the star's spectrum
by measuring the diameter of the star (which is easy to do) and noticing that it is getting smaller and smaller
by seeing how the luminosity of the star has been decreasing as it moves farther and farther away
by seeing the whole star become much redder than it used to be
the astronomer must be making up stories to impress his colleagues; there is no way to measure the speed with which stars move away or toward us.
Astronomers call the motion of a star across the sky (perpendicular to our line of sight) its
proper motion
Doppler Shift
light travel time
spectral type
radial velocity
Studies of the spectra of stars have revealed that the element that makes up the majority of the stars (75% by mass) is
hydrogen
stellarium
carbon
Einsteinium
helium
Which of the following can astronomers NOT learn from studying the spectrum of a star?
whether it is a star the size of the Sun or a giant star
its motion toward or away from us
its surface temperature
whether it is rotating slow or fast
you can’t fool me, all of the above can be learned from studying the spectrum
Most of the stars we can see with the unaided eye from Earth are
undergoing some sort of explosion which makes their outer layers unusually bright
only visible to our eyes because they actually consist of three or more stars blending their light together
very close to us (among the closest stars)
more luminous (intrinsically brighter) than the Sun
intrinsically fainter than the Sun
Some "superstars" give off more than 50,000 times the energy of the Sun. Why are there no such stars among the stars that are close to the Sun?
because such very luminous stars are extremely rare, and thus any small neighborhood in the Galaxy is unlikely to contain one of them
because conditions in the "neighborhood" of the Sun only permit low-mass (low luminosity) stars to form
because such superstars only give off a lot of energy for a year or so, before they die
because all stars in the vicinity of the Sun have planets, and planets rob a star of its brightness
because such superstars are really several hundred stars blending their light together (but so far away we can't distinguish individual stars); nearby stars are easy to separate
The most common kinds of stars in the Galaxy have
enormous masses compared to the Sun
diameters thousands of times greater than the Sun's
spectra that show they contain mostly carbon
a dozen or more stars in close orbit around them
low luminosity compared to the Sun
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
its apparent brightness
you can't fool me, all of these are quite easy to measure directly
its chemical composition
its temperature
its mass
Two star that are physically associated (move together through space) are called
first contact stars
brown dwarf pairs
binary stars
double stars
main sequence stars
Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?
Kepler's Third Law
Hubble's Law
Stefan-Boltzmann Law
Einstein's Law
Wien's Law
Stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called:
spectroscopic stars
red giants
main sequence stars
extras
brown dwarfs
Which of the following has the smallest mass?
a planet
the Sun
you can't fool me, all these have roughly the same mass
the smallest mass star that can still have fusion of hydrogen to helium in its core
a brown dwarf
Stars on the main sequence obey mass-luminosity relation. According to this relation,
the higher the mass, the higher the luminosity
the brightest stars are made of such light materials they hardly have any mass at all
bright stars have more mass around them in the form of planets, comets, and asteroids
actually, there is no mass-luminosity relation for main sequence stars
the lower the mass, the higher the luminosity
Why can astronomers not measure the diameters of stars directly?
stars are so bright, their light burns out all the delicate instruments we would use to measure their diameters
you can't fool me; measuring the diameter of any star is a relatively easy process
all stars change their diameters regularly, growing alternately larger and smaller
stars are all in binary systems, and we can only see the combined diameter of both stars
stars are so far away, we cannot resolve (distinguish) their diameters
For what type of star can astronomers measure the diameter with relative ease?
main sequence stars
visual double stars
eclipsing binary stars
white dwarf stars
any star that is not a brown dwarf
An HR Diagram plots the luminosity of stars against their:
diameter
location in the sky
age
mass
surface temperature
In an HR diagram, where can you see the spectral type of a star (whether it is an O type star or a G type star, for example)?
only in the red giant region
along the bottom (the horizontal axis)
along the right (vertical axis)
HR diagrams have nothing to say about spectral types
only on the main sequence
Where on the HR Diagram would we find stars that look red when seen through a telescope?
only near the top of the diagram and never near the bottom
only on the right side of the diagram and never on the left
only near the bottom of the diagram and never near the top
anywhere on the diagram
only near the left side of the diagram and never near the right
A team of astronomers discovers one of the most massive stars ever found. If this star is just settling down in that stage of its life where it will be peacefully converting hydrogen to helium in its core, where will we find it on the H-R diagram?
near the very top of the main sequence, in the upper left
a little bit below the Sun on the main sequence
among the supergiants, in the upper left
it could be anywhere on the diagram; we would need more information to determine its place
among the most brilliant of the white dwarfs, in the lower left
The apparent brightness of stars in general tells us nothing about their distances; we cannot assume that the dimmer stars are farther away. In order for the apparent brightness of a star to be a good indicator of its distance, all the stars would have to be:
at the same distance
a lot farther away than they presently are
the same luminosity
the same composition
by themselves instead of in binary or double-star systems
Kepler's Laws can give us the relative distance of objects in the solar system. To convert these relative distances into actual distances, we need to:
measure the mass of the Sun
measure the size of the Earth
measure the exact time it takes for the Earth to spin once on its axis
measure the length of the year exactly
measure the distance directly to any object orbiting the Sun
An astronomical unit is:
the distance covered by light in one year
the distance covered by light in one month
the time it takes for the solar system to turn once on its axis
the distance to the nearest star
the average distance between the Earth and the Sun
Today, astronomers can measure distances directly to worlds like Venus, Mars, the Moon, or the satellites of Jupiter by
bouncing radar beams off them
using the Hubble Space Telescope to triangulate with
sending graduate students out with very long tape measures
using x-ray telescopes
using Cepheid variable stars that lie behind the planets
Why did it take astronomers until 1838 to measure the parallax of the stars?
because cepheid variable stars had not been discovered earlier
because most stars are too faint to see without a good telescope
because no one before then could conceive of the Earth moving around the Sun
because the stars are so far away that their annual shift of position in the sky is too small to see without a good telescope
because detecting parallax requires measuring a spectrum, which only became possible in the 1830's
What is the baseline that astronomers use to measure the parallax (the distance) of the nearest stars?
the diameter of the Earth
the distance between the Earth and the Moon
the diameter of the Earth's orbit around the Sun
no one can measure parallax for the stars; only for planets in our solar system
the distance between observatories in Greenwich, England and Washington, DC
What is the closest star to the Sun?
we won't know the answer to this until we can travel to the stars
the Earth
Proxima Centauri
Sirius
Bernard's Star
Which of the following will show the smallest parallax shift?
the star, 51 Pegasi
the Moon
the star, Proxima Centauri
the Sun
Jupiter
A type of star that has turned out to be extremely useful for measuring distance is
the Cepheid variables
the stars that lie in the constellation of Orion
the eclipsing binaries
the main sequence stars
the white dwarf stars
The measurement of cosmic distances was helped tremendously by the discovery, in the early part of the 20th century, that in Cepheid variable stars, the average luminosity was related to:
the abundance of hydrogen in their atmosphere
their radial velocity
their parallax
their distance form the Sun
the length of time they took to vary
An astronomer is interested in a galaxy called M31, the nearest galaxy that resembles our Milky Way. It is about 2 million lightyears away. Which technique would be able to give us a distance to this galaxy?
radar reflections
Kepler's Laws
none of these would work
period-luminosity relation for Cepheid variables
parallax
If an astronomer wants to find the distance to a star that is not variable and is located too far away for parallax measurements, she can:
use the star's light curve
only throw up her hands in desperation; there is no way to even estimate the distance to such a star
use Kepler's laws as modified by Newton
find the star's luminosity class from its spectrum and read the luminosity from an HR Diagram
search for planets around the star since it is much easier to get the distance to planets
The luminosity class of a star tells an astronomer
whether or not the star is surrounded by planets
whether the star is close to us or far away
whether the star is a supergiant, a giant, or a main-sequence star
none of these
how long ago the star formed
Astronomers must often know the distance to a star before they can fully understand its characteristics. Which of the following properties of a star typically requires a knowledge of distance before it can be determined?
luminosity
apparent brightness
distance doesn't help with knowing any of these properties
radial velocity
temperature
How did Henrietta Leavitt “calibrate” her period-luminosity relationship for Cepheid variable stars? In other words, how did she make the general idea into a numerical rule?
by assuming that the Cepheids that appeared the brightest in the sky were closest to us
by measuring the Doppler shift in the spectral lines of Cepheids as they pulsated
by finding cepheids in star clusters whose distance was known in another way
by noting that the period was related to the luminosity in all stars
because the star closest to us is a Cepheid variable and we know its distance
Why do all stars spend most of their lives on the main sequence?
because in this stage, the processes inside the star do not generate any energy; thus the star can continue in this stage indefinitely
because the neutrinos created inside the Sun do not carry any energy away with them
because the fuel for energy production in this stage of the star's life is hydrogen; and that is an element every star has lots and lots of
because during this stage the star contracts from enormous size to a relatively small ball; this takes a long time
this is an unsolved problem in astronomy, and is an important project for the world’s largest telescopes to work on
Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?
O
A
G
K
Actually, all stars spend about the same amount of time on the main sequence.
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
its initial composition
the number of companion stars or planets orbiting it
its radial velocity (as measured from the spectrum)
its ability to fuse the element carbon into some other element
its mass
The event in the life of a star that begins its expansion into a giant is
the star's internal structure reaches equilibrium for the first time in its life
the core reaches a temperature of ten million degrees
it reaches the stage that astronomers call the zero-age main sequence
almost all the hydrogen in its core that was hot enough for fusion has been turned into helium
as much as 90% of the star explodes violently
When the outer layers of a star like the Sun expand, and it becomes a giant, which way does it move on the H-R diagram?
it moves horizontally, but stays on the main sequence
toward the lower right
toward the upper left
toward the upper right
toward the lower left
A type of star cluster that contains mostly very old stars is
an HII region
a stellar association
a galaxy
an open cluster
a globular star cluster
How are globular clusters distributed in our Milky Way Galaxy?
completely randomly: you never know where we will find one
only in the main spiral disk of the galaxy
mostly in a large spherical halo (or cloud) surrounding the flat disk of the Galaxy
only in the very center of the Galaxy, really crowded together
where the giant molecular clouds are found
As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first?
as the stars in a cluster are born at the same time; so they will all move off the main sequence at the same time, as they evolve
M type stars, which are the coolest
the O and B type stars
G type stars, like our Sun
the lowest mass stars, which have the least amount of fuel for fusion
An astronomy student, for her PhD, really needs to estimate the age of a cluster of stars. Which of the following would be part of the process she would follow?
search for planets like Jupiter around the stars in the center of the cluster
count the number of M type stars in the cluster
plot an H-R diagram for the stars in the cluster
measure the Doppler shift of a number of the stars in the cluster
search for x-rays coming from the center of the cluster
On an H-R diagram of a cluster of stars, which characteristic of the diagram do astronomers use as a good indicator of the cluster's age?
the coolest surface temperature for a star that they can measure
how high up on the main sequence M type stars are found
the number of M stars on the main sequence
the point on the main sequence where stars begin to "turn off" -- to move toward the red giant region
the lowest luminosity star that is visible in the cluster
The oldest structures in our Galaxy turn out to be
giant molecular clouds
open clusters
stellar associations
HII regions
globular clusters
When stars become giants, which of the following does NOT usually happen?
They lose a significant amount of mass from their outside layers
their outer envelopes expand significantly
their overall luminosities increase
their surface temperatures become lower than before
their mass grows significantly as they incorporate planets and interstellar matter near the star
Why is it easier for red giants to lose mass than main sequence stars?
you can’t fool me, stars lose the same amount of mass during every stage of their lives
red giants are much hotter on their surfaces, allowing gases to move away
red giants are so big, the gravity at their surface (that holds material to the star) is less
all red giants explode at the end of their lives
red giants are made of carbon and oxygen throughout, which escape more easily
Which of the following stages will our own Sun go through in the future:
spending a long time on the main sequence
expanding to become red giant
eventually fusing helium into carbon
giving off a planetary nebula
all of these
If stars with masses like our Sun’s cannot make elements heavier than oxygen, where are heavier elements like silicon produced in the universe?
this is an unsolved problem in astronomy; no one knows
heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle
these heavier elements were made in the Big Bang at the time the universe began, and have been part of the universe ever since
heavier elements are made in the cores of planets that are molten and hot when they form
heavier elements are made in the proto-planetary disks that accompany many newly forming stars
Which of the following statements about the life of a star with a mass like the Sun is correct?
the core of this star will be too massive to form a white dwarf
after the main sequence stage, there is no further fusion of hydrogen anywhere in the star
before the star dies, it will fuse dozens of elements in its core
as the star is dying, a considerable part of its mass will be lost into space
at the end of its life, the star will explode as a supernova
When a single star with a mass equal to the Sun dies, it will become a
neutron star
pulsar
white dwarf
burster
black hole
Which of the following stages will the Sun definitely go through as it gets older?
white dwarf
asymptotic giant branch star
the Sun will go through all of these things
red giant
horizontal branch star
Which of the following is a characteristic of degenerate matter in a white dwarf star?
the degenerate matter region is expanding as time passes, until it covers a region the size of the orbit of Mars
electrons and protons join together in the nucleus to make neutrons and neutrinos
the atoms drink, smoke, use bad language, and are attracted to the wrong kinds of particles
the electrons get as close to each other as possible and resist further compression
helium is actively fusing into carbon
A charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our Sun will ultimately become, long, long after it has turned into a white dwarf. Why is the astronomer on duty going to have a bit of a problem satisfying her request?
the universe is not even old enough to have produced any white dwarfs yet
astronomers only let people with PhD's look at these stellar corpses; it's like an initiation rite for those who become astronomers
all the old stars in our Galaxy are located in globular clusters and all of these are too far away to be seen with the kind of telescope a college or university campus would have
after a white dwarf cools off it becomes too cold and dark to emit visible light
after being a white dwarf, the Sun will explode, and there will be nothing left to see
The most stable (tightly bound) atomic nucleus in the universe is:
iron
carbon
technetium
hydrogen
uranium
When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can’t keep it stable as a white dwarf. Instead, it becomes:
a black dwarf
a red giant
a neutron star
a planetary nebula
a ball of solid iron, with layers of other elements around it
a neutron star is as dense as
the center of the Earth
a white dwarf star
the nucleus of an atom
our astronomy textbook
water
Which of the following is the smallest (in diameter)?
main sequence star
neutron star
white dwarf
red giant
protostar
Which of the following is the largest (in diameter)?
neutron star
white dwarf
main sequence star
red giant
black dwarf
After the core of a massive star becomes a neutron star, the rest of the star's material
is vaporized by the incredible heat of the dying star and evaporates
continues regular fusion and returns to the main sequence
falls inward very slowly, taking billions of years to get really compressed
makes a planetary nebula, which gently moves outward from the center
explodes outward as a supernova
Which of the following is NOT a result of supernova explosions?
a tremendous flood of high-energy cosmic ray particles is released
the neutron star is disrupted and tears apart into many pieces
any planets within a few dozen LY of the explosion are bathed with life-threatening radiation
new heavier elements (including such heavy nuclei lead and uranium) are fused by neutron bombardment during the explosion
many of the elements the star fused during its life are blasted out into space
Elements heavier than iron can be created during:
the big bang
the main sequence
a supernova explosion
astronomers don't have any idea of where these elements came from; it's an unsolved mystery
the subgiant phase of a star's life
When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's?
they are so large, their dark outline block a significant amount of starlight from behind themw
we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsar
some neutron stars soon collapse to be white dwarfs, whose light can be detected further away
astronomers have actually only found one neutron star and that was discovered very close to us and by sheer luck
they give off a lot more light than expected, and can be seen glowing with a reddish light from far away
What kind of telescope did Jocelyn Bell use to discover pulsars in 1968?
ultraviolet
radio
x-ray
visible light
neutrino
If a very distant galaxy looks blue overall to astronomers, from this they can conclude that:
the galaxy is moving toward us at great speed
the galaxy must not be especially massive when compared to most galaxies
the galaxy must have a lot of young stars and thus active star formation must still be going in it
the galaxy must be composed mostly of very old stars
the galaxy must have had a personal tragedy of some sort and needs a lot of love
With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that
the galaxy must be closer to us than 1 billion light years
the galaxy must contain a quasar
the galaxy must be a massive elliptical galaxy
the galaxy must have had an entire generation of stars that was born, lived, and died
what they are seeing is not a galaxy at all, but the remnant of one supernova
There is some irony in the fact that the Hubble Space Telescope has shown that Edwin Hubble’s classification scheme for galaxy shapes only works in the later stages of the universe. What have really deep pictures (going way back in time) taken with the Hubble Telescope shown about galaxies long ago (in the first few billion years after the Big Bang)?
you can’t fool me; the Hubble Space Telescope has a smaller mirror than the largest telescopes on the ground. We can’t use it to see galaxies that long ago.
long ago, all the galaxies were spiral shaped; there were no other shapes at all
long ago, galaxy shapes were not (for the most part) regular and organized; galaxies looks chaotic and lumpy
long ago, there were no galaxies at all; stars were evenly distributed through space and had not yet formed galaxies
long ago, galaxies were much larger than galaxies are today; those very large galaxies broke apart and made the galaxies we know
Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally:
bluer and smaller
redder and smaller
bluer and larger
redder and larger
pretty much the same
If we want to see what galaxies looked like at a time close to the beginning of the universe, where should we look?
near the center of the Virgo Cluster of galaxies
in a direction away from the plane of the Milky Way, where we can see very faint galaxies that are more than 10 billion light years away
within the nearest 100 million light years from the Milky Way
in the Local Group of galaxies
it doesn’t matter; you can look at any galaxy, because all galaxies look pretty much the same today as they did in the early days of the universe
One important way astronomers can learn in some detail about what happens when galaxies collide is
to examine the satellite galaxies presently orbiting the Milky Way
to look at videos of car accidents that are particularly violent
to watch the Andromeda Galaxy (M31,) which is on a collision course with us, for a decade
to simulate galaxy collisions on a large computer and watch what the simulation predicts
to look at the supermassive black hole at the center of the Milky Way
Why do galaxies collide, while stars almost never do?
stars are surrounded by planets, which prevent collisions; galaxies are not
stars don’t have very much mass, so their gravity is very small and can’t pull things well
actually, stars collide all the time, but astronomers don’t have any way of observing it
stars are so far apart that the chance of them colliding is essentially zero
stars have a very strong negative charge on them, so they repel other stars that get near
According to our current understanding, giant elliptical galaxies form:
by being located near the center of the Big Bang explosion and thus getting a major early push
when a black hole swallows enough material so that most of the stars in the galaxy are inside the black hole, leaving only a thin halo
only in the giant voids that astronomers are discovering among the filaments and chains of galaxies
by the merger (or swallowing) of a number of smaller galaxies in a cluster of galaxies
An astronomer discovers a massive galaxy which has four nuclei. What is a likely explanation for a galaxy having more than one nucleus?
the galaxy must have swallowed several smaller galaxies that were its neighbors
the galaxy must have had an unusual number of supernova explosions
the galaxy must have been a quasar earlier in its life
astronomers have no explanation for multiple nuclei in galaxies; it's baffling
the nuclei of galaxies often split into two or more parts because of internal activity
According to the Cosmological Principle, the universe
has no beginning and no end
is isotropic and homogeneous
consists only of galaxies that are exactly like the Milky Way
cannot be understood by the use of scientific observations alone
has all the galaxies arranged in groups about the size of our Local Group
Roughly how many galaxies make up our Local Group?
only three
about 60 or so
many hundreds
thousands
millions
How do astronomers know that there aren’t significant amounts of dark matter within our solar system?a
astronomers have now discovered quite a bit of dark matter in the solar system, so the premise of the question is wrong
the theory of dark matter, which now explains everything we want to know about it, tells us that it can only exist on the outside of galaxies
a lot of dark matter would affect the motions (orbits) of our spacecraft as the move through the solar system, and see no such effect
so much dark matter would affect the amount of energy coming out of the Sun, and we see no evidence for that
such dark matter would affect the weather patterns on Earth, and we see no such effect
Some astronomers searching for what the mysterious “dark matter” might be made of have pinned their hopes on MACHO’s (MAssive Compact Halo Objects). What do they think these MACHO’s are?
"cannibal galaxies” that have swallowed smaller galaxy neighbors until they have grown very large
black holes, brown dwarfs, and white dwarfs in the regions outside the main disk of our Galaxy
vast clouds of neutrinos, emitted by ancient supernovae
huge concentrations of antimatter, outside of galaxies
What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized?
galaxy groups make a huge spiral structure that resembles the Milky Way (but is much bigger)
galaxy groups are organized into huge filaments with great voids between them -- something like the structure one would see taking a cross-section of some soap bubbles
you can't fool me; astronomers cannot get any sense with our present-day instruments of how groups of galaxies are distributed on the large scale
galaxy groups are distributed completely evenly -- there is typically the same amount of space between them -- and so there is no structure evident
galaxy groups are organized into huge spherical "lumps" with concentric rings of groups of galaxies around each lump
The “great voids” that astronomers studying galaxies are finding are:
huge regions inside spiral galaxies, where the powerful radiation from a very hot star has cleared out the local interstellar material
very large regions of intergalactic space, where relatively few galaxies or galaxy clusters can be found
regions where a number of black holes have cleared out space in the center of a galaxy
empty regions between the spiral arms of the Milky Way Galaxy
